Sensors with movable parts are used in many applications, for example as acceleration sensors or as sound sensors, i.e. microphones. In some types of these sensors, a movable object is displaced with respect to two or more electrodes arranged close to the moving object, and change of capacitance between the movable object and the electrodes caused by this movement may be read out from the sensor. For example, the movable object may be a membrane of a microphone.
Such sensors may for example be implemented in the form of microelectromechanical systems (MEMS), which are also referred to as micro machines or systems based on microsystems technology.
As the signal provided by the sensor in many cases is comparatively weak, the signal is usually amplified before it is further processed.